WEDNESDAY, May 9 (HealthDay News) -- An increasing number of wheelchair breakdowns are causing people with spinal cord injuries to be left stranded, hurt or unable to keep their medical appointments, according to a new study.

In the report, published online in the American Journal of Physical Medicine & Rehabilitation, University of Pittsburgh researchers suggested that changes in Medicare reimbursements may be contributing to this growing problem.

The researchers found that more than half of wheelchair users had a breakdown within six months. A growing number of these breakdowns resulted in injuries and other health and safety concerns.

In conducting the research, Dr. Michael Boninger, of the University of Pittsburgh's physical medicine and rehabilitation department, and colleagues examined an ongoing survey study of more than 700 people with spinal cord injury who were confined to a wheelchair for a minimum of 40 hours each week. The participants provided information on the wheelchair problems they experienced and what happened as a result of their breakdowns.

The study revealed that the rate of wheelchair breakdowns surged between 2006 and 2011. During this time, roughly 53 percent of wheelchair users reported at least one breakdown requiring repairs within six months -- up from 45 percent between 2004 and 2006. The average number of repairs per person also surged from 1.03 in 2004-2006 to 1.42 in 2006-2011.

"It is possible that this increase in the number of repairs is the result of a decrease in wheelchair quality resulting from changes in reimbursement policies and a lack of enforcement of standards testing," the study authors noted in a journal news release.

The researchers also found the rate of adverse consequences of breakdowns jumped to 30.5 percent in 2006-2011 from 22 percent in 2004-2006. The total number of consequences per wheelchair user was also twice as high.

Power wheelchairs, particularly those with power seats, were more problematic than manual models, accounting for almost two-thirds of all problems reported by users.

Racial and ethnic minorities reported a greater number of breakdowns. The study authors pointed out that these patients were also less likely to have a backup wheelchair available to them.

Moreover, the study showed wheelchairs paid for by Medicare or Medicaid had higher rates of breakdowns and resulting problems than those covered by private insurance or other sources, including the Veterans Administration.

The study warned that lenient requirements for testing do not ensure that wheelchairs meet certain safety or performance standards.

"This paper should serve as a call to reevaluate and revise current policies and standards testing for wheelchair prescription in the United States," said Boninger's team. The researchers added that informing wheelchair users about the importance of routine wheelchair maintenance could help reduce breakdowns and avoid injuries.